PROJECT SUMMARY/ABSTRACT Polycystic ovary syndrome (PCOS) is a complex endocrine disorder of women characterized by androgen excess, menstrual irregularity and polycystic ovaries. Affecting 6-10% of reproductive-aged women, 60?95% of PCOS women have insulin resistance that is exaggerated by increased total and abdominal fat deposition, predisposing to metabolic syndrome and diabetes as risk factors for cardiovascular disease (CVD). Of concern, androgen excess in PCOS women who are normal-weight is closely linked with preferential abdominal fat deposition and increased intra-abdominal fat mass that is positively correlated with serum fasting insulin and lipid levels. Moreover, androgen excess in these PCOS women also is accompanied by a greater proportion of small adipocytes (fat cells) in subcutaneous (SC) abdominal adipose where fat is normally stored. Therefore, normal-weight PCOS women may have a reduced capacity of SC adipose to safely store fat. When energy intake exceeds that capacity, SC abdominal adipocytes may overfill with lipid and promote excess lipid deposition in abnormal (ectopic) locations, where increased oxidative stress underlies metabolic dysfunction (i.e., lipotoxicity). We hypothesize that androgen excess in normal-weight PCOS women alters SC abdominal adipogenesis, defined as the ability of adipose stem cells to develop into mature adipocytes and, in doing so, impairs metabolic function. Further, these androgen actions may originate from heritable changes in the genes of these stem cells or their developing adipocytes without affecting the DNA sequence of the genes themselves (i.e. epigenetic). In this NCTRI Project IV renewal, we will 1) examine molecular mechanisms of SC abdominal adipogenesis in normal-weight PCOS women compared to weight- and age-matched normoandrogenic ovulatory women (controls), 2) determine the role of androgen action in SC abdominal stem cell dysfunction and its relationship to metabolism in these PCOS women receiving the antiandrogen, flutamide or placebo through a clinical trial and 3) identify crucial epigenetic changes that distinguish SC abdominal stem cells in such PCOS women compared to those of weight- and age-matched control women. Understanding androgen action during SC abdominal adipogenesis in normal-weight PCOS women and its adverse effects on metabolic function through stem cell differentiation allows development of new and personalized clinical strategies, including stem cell therapies and pharmacological interventions, that could improve metabolic function in PCOS women and decrease their susceptibility to CVD.